TOKYO--A message Japan began delivering Monday is a bit unusual, but true enough: Don't wait until it's too late to think about toilet paper.

The government and paper companies kicked off a "Let's stockpile toilet paper!" campaign to mark Disaster Prevention Day, warning of a possible crisis because nearly half of the supply comes from one of Japan's most earthquake-prone areas.

Officials said people immediately think of food and water as emergency supplies, but easily forget toilet paper, and get desperate when it's too late.

"After running out of toilet paper, people start using tissue, and that could clog up precious workable toilets," said Toshiyuki Hashimoto, an industry ministry official in charge of paper products.

As part of the campaign, makers are offering a tightly rolled, 150-meter- (490-foot) long, single-layer toilet paper that lasts more than twice as long as a regular roll.

A family of four should be able to survive for a month on a six-roll pack, priced at 460 yen (US$4.40) and with a five-year expiration date, said Satoshi Kurosaki, chairman of the Japan Household Paper Industry Association.

Government and industry officials said 41 percent of the country's toilet paper supply comes from Shizuoka prefecture in central Japan, where experts say there is a higher than 80 percent chance of a major offshore quake in the next 30 years.

Officials warned of a nationwide toilet paper shortage for about a month in such a disaster, based on lessons learned from the deadly March 2011 earthquake and tsunami in northern Japan.

Nine months after that disaster, toilet paper was added to a list of recommended items that included food, water, portable toilets and a first-aid kit, under the government's Basic Disaster Management Plan.

"Along with food, toilet paper was among the first items that disappeared from store shelves during the disaster, even outside disaster-hit areas," Hashimoto said in front of a public display in the ministry entrance hall, decorated with campaign posters, including one saying "Be prepared and no regrets!"